Liquid hydrocarbon jet fuels containing hydrocarbon phosphines



Patented .lan. 22, i363 ice 3,074,230 LIQUID HYDRGCARBUN JET FUELS Q'SNTAHNENQ EYDRGCARBGN PHQSPHHNES Albert N. De Vault, Bartiesville, Okla, assignor to Philiips Petroleum Company, a corporation of Delaware No Drawing. Filed May 15, 1958, Ser. No. 735,306 3 Claims. (Cl. 60--35.4)

This invention relates to improved rocket fuels. In one aspect it relates to non-leaded rocket fuels containing a stability additive.

Petroleum fractions used for blending rocket fuels, such as jet fuels, are unstable at the elevated temperatures encountered in rocket and jet engines of advanced design operating at supersonic flight speeds. For example, it has been found that the decomposition products of the jet fuels foul heat exchangers and plug fuel-system filters. At temperatures up to about 400 F. many of the usual detergent-dispersant type additives are effective in alleviating the problems of deposits and filterability, however, at higher temperatures these additives tend to promote deposit formation and plug fuel-system filters.

It is an object of this invention to provide improved rocket fuels.

Another object of this invention is to provide nonleaded rocket fuels having improved stability.

Still another object of this invention is to provide a method for reducing fouling in rockets and jet engines.

Yet another object of the invention is a method for reducing fouling of heat exchangers and fuel filters in jet engines employing non-leaded fuels.

These and other objects of the invention will become more readily apparent from the following detailed description and discussion.

The compositions of this invention comprise non-leaded hydrocarbon fuels, i.e. hydrocarbon fuels which do not contain tetraethyl lead, suitable for use in rockets and jet engines, containing a compound having the formula wherein R R and R are selected from the group consisting of alkyl, alkaryl, aryl and aralkyl radicals, and R R and R can be different radicals.

The invention will be described by particular reference to jet fuels and jet engines. This is not intended, however, in any way to limit the scope of the invention, which is applicable to rockets and rocket fuels in general.

Examples of stabilizing compounds which can be used in the composition of this invention include triethylphosphine, trixylylphosphine, tributylphosphine, di'butylphenylphosphine, methylethylbutylphosphine, dixylylphenylphosphine, dihexylmethylphosphine, triphenylphosphine, diethylpropylphosphine, 2-ethylphenylbutylhexylphosphine, trioctylphosphine, 2,3-dimethyltolyldiethylphosphine, dimethyldecylphosphine, 1-propylxylyldiphenylphosphine, tri-(l,3-dipropyl cresyl) phosphine, tritolylphosphine, triheyptylphosphine, triisopropylphosphine, tricresylphosphine, tritertiarybutylphosphine, diphenyltolylphosphine, etc. While alkyl and aryl substituted triphosphines in general can be used, the preferred compounds are those in which each alkyl group contains not more than 7 carbon atoms and each alkaryl, aryl and aralkyl group con tains not more than 15 carbon atoms.

The amount of phosphine employed will vary depending on the particular additive used and the rocket fuel to which it is added. Usually the quantity of'stabilizing agent varies between about 0.04 and about 1.0 percent by weight of the fuel andmore preferably between about 0.07 and about 0.20 percent by weight; however, quantities outside of these ranges can be employed to provide the desired stabilizing effect.

let fuels which are stabilized in the method of this invention include fuels, such as JP3, JP-4, JP-S, and JP-S, which are commonly employed in jet engines at the present time. These fuels are almost entirely derived from and made up of petroleum hydrocarbons together with minor amounts of other additives which may be added for the purpose of improving the characteristics of, or the performance of the fuel. The petroleum hydrocarbons which are used include not only crude oil, but also gas oil, residual oil and oils derived from shale, tars, and the like. Jet fuels can also be prepared by admixture of synthetic hydrocarbon oils. Commonly, these jet fuels boil between and 600 F., have API gravities of 35 to 60 degrees and possess Reid vapor pressure of 0.0 to 7 psi Specifications for representative fuels are tabulated below.

Jet fuels Rocket fuel, Specification RP-l JP-3 IF-4 JP-5 JP6 Gravity range, API- 50-60 45-57 3648 3750 42-54 Reid vapor pressure, p.s.i. 5-7 2-3 Flash point, F., miuimum 140 Distillation, maximum percegfodistilled at temp. F.:

Maximum volume percent:

410 F. 2 End point 525 F.).

The fuels used inthe operation of jet engines are subjected to relatively high temperatures in their passage from the fuel tank through various parts of the jet engine into the combustion chamber; for example, in the operation of a ram-jet the various fuel lines are exposed to air entering the jet, which at'Mach 2 may have a temperature as high as 400 F., and at Mach 4 a temperature as high as 1000 F. In addition, the fuel before entering the jet engine combustion chamber is often used to cool the jet engine lubricating oil, which further increases the fuel temperature. As previously set'forth at fuel temperatures up to about 400 F. many of the usual detergentdispersant type additives are effective in alleviating the problems which result from fuel decomposition; however, at higher temperatures this type of additive can promote deposit formation and the plugging of the fuel system. Also, these additives are not suitablefor use in systems where water is present, for example fuel storage systems which are flushed or displaced with water. It has been found that trisubstituted phosphines, wherein the substituent groups are selectedfrom'the group consisting of alkyl, alkaryl, aryl and aralkyl, are effective in stabilizing petroleum hydrocarbon jet fuels and preventing deposits in aovaaeo the jet engine, not only at lower temperatures, but also at temperatures above 400 F. In addition these additives are particularly suitable for use in the presence of water.

Frequently, it is diificult and uneconornical to test fuels under actual operating conditions in a jet engine. For this reason, apparatus has been designed for the purpose of carrying out equivalent tests in a laboratory installation. These tests are conventionally carried out in an apparatus designated as a CFR Fuel Coker. The method which is utilized in conjunction with this apparatus has been designated as Tentative Standard Method 3464 T. This method is a part of Federal Test Method Standard, Number 791 (formerly Federal Specification VV- L-791). The title given to this test is Thermal Stability of Gas Turbine Fuels.

The CFR Fuel Coker (manufactured by ERDCO Engineering Corp., Addison, Illinois) is a laboratory apparatus designed to measure the high temperature stability of jet fuels. In principle, it subjects the test fuel to the same level of temperature stress in a mariner similar to that occurring in jet engines. Schematically, the engine consists of a fuel system with two heated sections, a preheater section and a filter section. The preheater section simulates the hot fuel line sections of the engine as typified by an engine fuel oil cooler. The filter section represents the nozzle area of the engine where fuel degradation particles may become trapped. Details on the construction and operation of the CFR Fuel Coker are given in Coordinating Research Council Inc., Manual Number 3, dated March 1957. This manual was prepared under CRC Project Number CFA-2-54.

The deposits which occur during the testing of jet fuels in the CFR Fuel Coker are resinous or lacquer type deposits. These deposits range in color from light amber to black and the progression of color changes from amber to black with increasing preheater temperature. A visual method has been developed for rating the various deposits (Tentative Standard Method 3464-T, page 24), and is set forth in the table below.

Deposit identity: Numerical rating No visible deposits M w Haze or dulling, no color 1 'Barely visible discoloration.. 'i 2 Light tan 3 Heavier than 3 4 EXAMPLE I In a beaker test a raw kerosene when heated to 380 F. maximum temperature became yellow in color, accompanied by the formation of colloidal insoluble material. When the test was repeated with kerosene containing 0.1 percent by weight of triphenylphosphine, evidences of thermal instability were absent. The color of the kerosene with the triphenylphosphine added remained good and no insolubles were formed.

EXAMPLE II Triphenylphosphine was heated in liquid petrolatum at temperatures over 560 F. and remained stable.

EXAMPLE III A IP-S fuel was tested in a Model O1FC (Manual) CFR Fuel Coker at 400 F. preheater temperature; 500 F. filter block temperature; maximum filter pressure of 25.0 inches of Hg and a fuel rate of 6 pounds per hour.

utes respectively; however, by means of a by-pass around the filter, fuel was circulated through the preheater tube for the full 300 minutes in eac 1 run.

2 Mixture of metal deactivator (30% N,N-disalicylidene-1,2-diamin0 propane plus 20% xylene) and sludge dispersant (8% lauryl methacrylate plus 20% diethylaminoethylmethacrylate). 50 ppm. is recommended by manufacturer for optimum results. This was confirmed by tests carried out at different concentrations of this additive.

3 19 gm. in 5 gal. of fuel (0.38 gin/ ml).

From the data in Table 1, it is apparent that tri-n-butylphosphine substantially eliminated deposits in both the filter section and in the pre-heater tube.

EXAMPLE IV A raw kerosene was tested in the same apparatus as Example III under the same temperature conditions, same maximum filter pressure and at the same feed rate, with the following results:

Table 2 Additive,

weight Filter time, Filter Preheater percent minutes pressure, tube triphenylinches Hg rating phosphine It is noted from the data in Table 2 that with 0.05 percent additive and higher the filter pressure remained substantially below the maximum of 25 inches Hg ever: after 300 minutes of operation. With 0.100 weight percent additive, no deposits were obtained in the prehenter tube.

EXAMPLE V Water tolerance tests were carried out on phosphines in kerosene according to ASTM Test D-1 094, as modified by Wright Air Development Center. In this test water tolerances are rated as follows:

Class (1)Clear and clean 7 Class (2)Shred of lace and/or film at interface Class (3)Loose lace and/or slight scum Class (4)-Tight lace and/or heavy scum The results of the tests are set forth in Table 3.

Table 3 Class Vol. change Ker 1 1.5 Kerosene plus 0.1 g./100 ml. triphenylphosphine.-- 1 1. 0 Kerosene plus 0.1 g./100 m1. tri-n-butylphosphine. 1 1.0

It is apparent from the data that emulsification of kerosene with water is eliminated by the phosphine additive. Thus, this additive provides an advantage for use in fuel storage systems which are flushed or displaced with water, such as the fuel tanks of an aircraft carrier.

Having thus described the invention by providing specific examples thereof, it is to be understood that no undue limitations or restrictions are to be drawn by rea son thereof and that many variations and modifications are within the scope of the invention.

I claim:

1. In the operation of a jet engine using a non-leaded liquid hydrocarbon jet fuel the method for reducing deposits in said jet engine which comprises introducing to said engine a fuel comprising as its major component a non-leaded liquid hydrocarbon jet fuel having the boiling range of kerosene and containing an amount suflicient to reduce said deposits of a compound having the formula wherein R R R are selected from the group consisting of alkyl, alkaryl, aryl and aralkyl radicals, and R R and R, can be different radicals.

2. The process of claim 1 wherein said compound consists of between about 0.04 and about 1.0 percent by weight of triphenylphosphine.

3. The process of claim 1 wherein said compound consists of between about 0.04 and about 1.0 percent by weight of tributylphosphine.

4. In the operation of a jet engine using a kerosene fuel the method for reducing deposits in said jet engine which comprises introducing to said jet engine a non-leaded jet fuel comprising as its major component kerosene containing between about 0.04 and about 1.0 percent by Weight of a compound having the formula References Cited in the file of this patent UNITED STATES PATENTS 1,575,440 Midgley Mar. 2, 1926 2,149,271 Butz Mar. 7, 1939 2,265,819 Rosen Dec. 9, 1941 2,274,291 Clayton et al Feb. 24, 1942 2,368,866 Nygaard et al Feb. 6, 1945 2,797,153 Bereslavsky June 25, 1957 2,828,195 Yust et a1 Mar. 25, 1958 2,892,305 Zletz et al. June 30, 1959 OTHER REFERENCES Barnard: Petroleum Processing, pp. 1229 to 1232 (November 1951). 

1. IN THE OPERATION OF A JET ENGINE USING A NON-LEADED LIQUID HYDROCARBON JET FUEL THE METHOD FOR REDUCING DEPOSITS IN SAID JET ENGINE WHICH COMPRISES INTRODUCING TO SAID ENGINE A FUEL COMPRISING AS ITS MAJOR COMPONENT A NON-LEADED LIQUID HUDROCARBON JET FUEL HAVING THE BOILING RANGE OF KEROSENE AND CONTAINING AN AMOUNT SUFFICIENT TO REDUCE SAID DEPOSITS OF A COMPOUND HAVING THE FORMULA 